Multi-stage reforming process with final stage catalyst regeneration

ABSTRACT

The present invention relates to a multistage reforming process to produce a high octane product. A naphtha boiling range feedstock is processed in a multi-stage reforming process, in which said process involves at least 1) a penultimate stage for reforming the naphtha feedstock to produce a penultimate effluent 2) a final stage for further reforming at least a portion of the penultimate effluent 3) a regeneration step for the final stage catalyst. The severity of the penultimate stage can be increased during final stage catalyst regeneration in order to maintain the target RON of the reformate product and avoid reactor downtime.

RELATED APPLICATION

This application claims priority to U.S. patent application Ser. No.12/134,153, filed Jun. 5, 2008. This application claims priority to andbenefits from the foregoing, the disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to a multistage reforming process withminimized down time during final stage catalyst regeneration. Theprocess uses a medium pore molecular sieve catalyst in the final stageto enable fast regeneration without a halogenation step.

BACKGROUND OF THE INVENTION

Catalytic reforming is one of the basic petroleum refining processes forupgrading light hydrocarbon feedstocks, frequently referred to asnaphtha feedstocks. Products from catalytic reforming can include highoctane gasoline useful as automobile fuel, aromatics (for examplebenzene, toluene, xylenes and ethylbenzene), and/or hydrogen. Reactionstypically involved in catalytic reforming include dehydrocylization,isomerization and dehydrogenation of naphtha range hydrocarbons, withdehydrocyclization and dehydrogenation of linear and slightly branchedalkanes and dehydrogenation of cycloparaffins leading to the productionof aromatics. Dealkylation and hydrocracking are generally undesirabledue to the low value of the resulting light hydrocarbon products.

Catalysts commonly used in commercial reforming reactions often includea Group VIII metal, such as platinum or palladium, or a Group VIII metalplus a second catalytic metal, which acts as a promoter. Examples ofmetals useful as promoters include rhenium, tin, tungsten, germanium,cobalt, nickel, rhodium, ruthenium, iridium or combinations thereof. Thecatalytic metal or metals may be dispersed on a support such as alumina,silica, or silica-alumina. Typically, a halogen such as chlorine isincorporated on the support to add acid functionality. In addition toGroup VIII metals, other reforming catalysts include aluminosilicatezeolite catalysts. For example, U.S. Pat. Nos. 3,761,389, 3,756,942 and3,760,024 teach aromatization of a hydrocarbon fraction with a ZSM-5type zeolite catalyst. U.S. Pat. No. 4,927,525 discloses catalyticreforming processes with beta zeolite catalysts containing a noble metaland an alkali metal. Other reforming catalysts include other molecularsieves such as borosilicates and silicoaluminophosphates, layeredcrystalline clay-type phyllosilicates, and amorphous clays.

In addition to selection of catalysts for reforming, various processesfor reforming a naphtha feedstock in one or more process steps toproduce higher value reformate products are known in the art. U.S. Pat.No. 3,415,737 teaches a process for reforming naphtha under conventionalmild reforming conditions with a platinum-rhenium-chloride reformingcatalyst to increase the aromatics content and octane number of thenaphtha. In U.S. Pat. No. 3,770,614 there is disclosed a process inwhich a reformate is fractionated and the light reformate fraction (C6fraction) passed over a ZSM-5-type zeolite to increase aromatic contentof the product. U.S. Pat. No. 3,950,241 discloses a process forupgrading naphtha by separating it into low- and high-boiling fractions,reforming the low-boiling fraction, combining the high-boiling naphthawith the reformate, and contacting the combined fractions with aZSM-5-type catalyst. U.S. Pat. No. 4,181,599 discloses a process forreforming naphtha comprising separating the naphtha into heavy and lightfractions and reforming and isomerizing the naphtha fractions. U.S. Pat.No. 4,190,519 teaches a process for upgrading a naphtha-boiling-rangehydrocarbon which comprises separating the naphtha feedstock into alight naphtha fraction containing C6 paraffins and lower-boilinghydrocarbons and a heavy naphtha fraction containing higher-boilinghydrocarbons, reforming the heavy naphtha fraction and passing at leasta portion of the reformate together with the light naphtha fraction overa zeolite catalyst to produce an aromatics-enriched effluent. Differentcatalysts may be employed in different process steps during thereforming of naphtha feedstocks as described in U.S. Pat. No. 4,627,909,U.S. Pat. No. 4,443,326, U.S. Pat. No. 4,764,267, U.S. Pat. No.5,073,250, U.S. Pat. No. 5,169,813, U.S. Pat. No. 5,171,691, U.S. Pat.No. 5,182,012, U.S. Pat. No. 5,358,631, U.S. Pat. No. 5,376,259 and U.S.Pat. No. 5,407,558, for example.

Even with the advances in naphtha reforming catalysts and processes, aneed still exists to develop new and improved reforming methods toprovide higher liquid yield, improve hydrogen production, and minimizethe formation of less valuable low molecule weight (C₁-C₄) products. Ithas been discovered that interstage feed separation in a stagedreforming process and lower pressure in the final stage of a multistagereforming process can improve the RON (Research Octane Number),aromatics content, C₅+ liquid yield, hydrogen production, and catalystlife.

SUMMARY OF THE INVENTION

The present invention is based on the discovery that in a multi-stagereforming process, the yield of hydrocarbon product and hydrogen can beoptimized by increasing the severity of the penultimate stage duringregeneration of the final stage catalyst. During regeneration of thefinal stage catalyst, the RON of the effluent from the penultimate stagecan meet the target RON of the hydrocarbon product by temporarilyincreasing the severity of the penultimate stage reaction conditions.Due to fast regeneration times of the final stage catalyst, the lifetimeof the penultimate stage catalyst is minimally affected by the increasedreaction severity.

The present invention relates to processes for catalytically reforming anaphtha feed to produce a product reformate in a multistage reformingoperation. The reforming process includes providing a naphtha to amulti-stage reforming system that includes a penultimate reforming stagecontaining a first reforming catalyst and a final reforming stagecontaining a second reforming catalyst; contacting the naphtha at afirst reforming temperature with the first reforming catalyst andproducing a penultimate effluent; contacting at least a portion of thepenultimate effluent at a second reforming temperature with the secondreforming catalyst and producing a final reformate having an RON ofgreater than 90; and regenerating the second reforming catalyst in thefinal reforming stage while reforming the naphtha in the penultimatereforming stage and producing a third reformate from the penultimatereforming stage that has an RON of at least 90.

In embodiments, the first reforming catalyst includes platinum andrhenium on an alumina support. In embodiments, the second reformingcatalyst includes silicalite having a silica to alumina molar ratio ofat least 200, a crystallite size of less than 10 microns and an alkalicontent of less than 5,000 ppm.

In embodiments, the step of regenerating the second reforming catalystincludes ceasing the flow of intermediate reformate to the finalreforming stage; increasing the reforming temperature in the penultimatereforming stage by at least 5° F. (2.8° C.) to produce a third reformatehaving an RON of at least 90; and regenerating the second reformingcatalyst in the final reforming stage. In further embodiments, the stepof regenerating the second reforming catalyst includes passing anitrogen containing stream through the second reforming stage to removeat least a portion of the naphtha container therein; passing an oxygencontaining stream through the final reforming stage to remove at least aportion of the carbon deposited on the second reforming catalystcontained within the final reforming stage; passing a nitrogencontaining stream through the second reforming catalyst to remove atleast a portion of the oxygen contained therein; reducing thetemperature of the second reforming catalyst within the final reformingstage to a temperature of less than the second reforming temperature;introducing at least a portion of the penultimate effluent to the finalreforming stage; and increasing the temperature of the second reformingcatalyst to a temperature in the range of 800° F. to 1100° F. (427°C.-593° C.). In further embodiments, the step of regenerating the secondreforming catalyst includes reducing the reforming temperature in thepenultimate reforming stage by at least 5° F. (2.8° C.).

Other aspects, features and advantages will be apparent from thedescription of the embodiments thereof and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of the invention.

FIG. 2 is a schematic diagram of a second embodiment of the invention.

DETAILED DESCRIPTION

In the present process, a naphtha boiling range feedstock is processedin a multi-stage reforming process, in which said process involves atleast a penultimate stage for reforming the naphtha feedstock to producea penultimate effluent and a final stage for further reforming a portionof the penultimate effluent. The reforming process is operated atconditions and with catalysts selected for conductingdehydrocyclization, isomerization and dehydrogenation reactions ofparaffins thus converting low octane normal paraffins and cycloparaffinsinto high octane materials. In this way, a product having increasedoctane and/or containing an increased amount of aromatics is produced.In preferred embodiments, the multi-stage reforming process is operatedat conditions and with one or more catalysts for producing a netpositive quantity of hydrogen. It is a further object of the inventionto provide for a regeneration step during which the final stage catalystis regenerated while reformate product of a target RON is produced bytemporarily increasing the severity of the penultimate stage such thatthe effluent of the penultimate stage comprises reformate of the targetRON.

The multi-stage reforming process of the invention comprises passing arefinery stream through at least two reforming stages in series. Ingeneral, each reforming stage is characterized by one or more reformingreactor vessels, each containing a catalyst and maintained at reformingreaction conditions. The product from each stage before the final stageis passed, at least in part, to the succeeding stage in the multi-stageprocess. The temperature of the product from each stage which is passedto a succeeding stage may be increased or decreased to meet theparticular needs of the process. Likewise, the pressure of the productwhich is passed to a succeeding stage before the final stage may beincreased or decreased. Preferably the final stage is run at a lowerpressure than the penultimate stage.

The present invention is based in part on the discovery that selectivereforming of C5-C8 paraffins in a separate or additional reforming stageprovides improved performance of the overall reforming process. Thus, apenultimate reforming stage using a conventional reforming catalyst isoperated at relatively low severity, since it is not required to reachthe high octane levels normally desired for a naphtha fuel or fuel blendstock. While not being bound to any theory, we believe that under theseconditions the reforming catalyst of the penultimate stage catalyzes themore facile reactions, such as cyclohexane and alkycyclohexanedehydrogenation, while keeping hydrocracking to a minimum. Generally, aconventional catalyst used to dehydrocyclize paraffins under more severeconditions produces higher quantities of light C1-C4 gases, on accountof the catalyst being somewhat unselective for dehydrocyclization. Withthe present invention, however, an intermediate reformate comprising atleast 70 vol. % C5-C8 hydrocarbons from a penultimate reforming stage ispassed to a final reforming stage containing the same or a differentreforming catalyst as the penultimate stage. The C9+ fraction from thepenultimate stage has higher octane than the C5-C8 fraction, and is notfurther reformed in the final stage, thus preventing any unwanteddealkyation or cracking of the C9+ hydrocarbons. In a preferredembodiment the final stage is run at a lower pressure than thepenultimate stage. We believe that running the final stage at a lowerpressure than the penultimate stage leads to improvements including oneor more of the following characteristics—1) increased yield of C5+liquid products, 2) minimized unwanted hydrocracking/dealkylationreactions, and 3) increased hydrogen production. Lower pressure of thefinal stage can, in some cases, lead to higher catalyst fouling ratesdepending on the type of catalyst used; however, in situ catalystregeneration of the final stage catalyst can be used to maintaincatalyst activity. While the final stage catalyst is being regenerated,the severity of the penultimate stage can be temporarily increased tomeet octane targets for the total blended reformate which wouldotherwise be achieved with both the penultimate and final stagesoperating. Consequently, the performance characteristics of thepenultimate and final stage reactors provide complementary benefits,resulting in an overall process which produces a high octane product atan improved C5+ liquid yield and improved hydrogen production.

While the discussion which follows relates at times, for convenience, tooperation of penultimate and final reforming stages, the principles ofthe invention are applicable as between any two successive stages andcan be applied to several sequentially connected stages. In essencethen, the term final stage as used herein does not necessarily indicatethe last stage if there are three or more stages, but rather indicates asucceeding stage which follows a preceding (often referred to forconvenience as “penultimate”) stage.

As disclosed herein, boiling point temperatures are based on ASTM D-2887standard test method for boiling range distribution of petroleumfractions by gas chromatography, unless otherwise indicated. Themid-boiling point is defined as the 50% by volume boiling temperature,based on an ASTM D-2887 simulated distillation.

As disclosed herein, carbon number values (i.e. C₅, C₆, C₈, C₉ and thelike) of hydrocarbons may be determined by standard gas chromatographymethods.

As disclosed herein, Research Octane Number (RON) is determined usingthe method described in ASTM D2699.

Unless otherwise specified, as used herein, feed rate to a catalyticreaction zone is reported as the volume of feed per volume of catalystper hour. The feed rate as disclosed herein is reported in reciprocalhours (i.e. hr-1) which is also referred to as liquid hourly spacevelocity (LHSV).

As used herein, a C₄− stream comprises a high proportion of hydrocarbonswith 4 or fewer carbon atoms per molecule. Likewise, a C₅+ streamcomprises a high proportion of hydrocarbons with 5 or more carbon atomsper molecule. It will be recognized by those of skill in the art thathydrocarbon streams in refinery processes are generally separated byboiling range using a distillation process. As such, the C₄− streamwould be expected to contain a small quantity of C₅, C₆ and even C₇molecules. However, a typical distillation would be designed andoperated such that at least about 70% by volume of a C₄− stream wouldcontain molecules having 4 carbon atoms or fewer per molecule. Thus, atleast about 70 vol % of a C₄− stream boils in the C₄− boiling range. Asused herein, C₅+, C₆-C₈, C₉+ and other hydrocarbon fractions identifiedby carbon number ranges would be interpreted likewise. In embodiments,the naphtha that is provided to the multi-stage reforming system has anRON of less than 80 or less than 75.

As used herein, the multi-stage reforming system includes at least tworeaction stages, a first (i.e. penultimate) containing a first reformingcatalyst and a second (i.e. final) containing a second reformingcatalyst. Included in the reforming system are the necessary heaters andfurnaces, valves, piping and associated hardware, and fractionationzones that are necessary for successful operation of the reformingsystem.

The term “silica to alumina ratio” refers to the molar ratio of siliconoxide (SiO2) to aluminum oxide (Al₂O₃).

As used herein the term “molecular sieve” refers to a crystallinematerial containing pores, cavities, or interstitial spaces of a uniformsize in which molecules small enough to pass through the pores,cavities, or interstitial spaces are adsorbed while larger molecules arenot. Examples of molecular sieves include zeolites and non-zeoliticmolecular sieves such as zeolite analogs including, but not limited to,SAPOs (silicoaluminophosphates), MeAPOs (metalloaluminophosphates),AlPO4, and ELAPOs (nonmetal substituted aluminophosphate families).

When used in this disclosure, the Periodic Table of the Elementsreferred to is the CAS version published by the Chemical AbstractService in the Handbook of Chemistry and Physics, 72nd edition(1991-1992).

As used herein, naphtha is a distillate hydrocarbonaceous fractionboiling within the range of from 50° (10° C.) to 550° F. (288° C.). Insome embodiments, naphtha boils within the range of 70° (21° C.) to 450°F. (232° C.) or within the range of 80° (27° C.) to 400° F. (204° C.) oreven within the range of 90° (32° C.) to 360° F. (182° C.). In someembodiments, at least 85 vol % of naphtha boils within the range of from50° (10° C.) to 550° F. (288° C.) or within the range of from 70° (21°C.) to 450° F. (232° C.). In embodiments, at least 85 vol % of naphthais in the C4-C12 range, or in the C5-C11 range, or in the C6-C10 range.Naphtha can include, for example, straight run naphthas, paraffinicraffinates from aromatic extraction or adsorption, C6-C10 paraffin-richfeeds, bioderived naphtha, naphtha from hydrocarbon synthesis processes,including Fischer Tropsch and methanol synthesis processes, as well asnaphtha from other refinery processes, such as hydrocracking orconventional reforming.

The reforming catalyst used in the penultimate reforming stage may beany catalyst known to have catalytic reforming activity. In oneembodiment, the penultimate stage catalyst comprises a Group VIII metaldisposed on an oxide support. Examples of Group VIII metals includeplatinum and palladium. The catalyst may further comprise a promoter,such as rhenium, tin, tungsten, germanium, cobalt, nickel, iridium,rhodium, ruthenium, or combinations thereof. In some such embodiments,the promoter metal is rhenium or tin.

The above mentioned metals can be disposed on a support comprising oneor more of (1) a refractory inorganic oxide such as alumina, silica,titania, magnesia, zirconia, chromia, thoria, boria or mixtures thereof;(2) a synthetically prepared or naturally occurring clay or silicate,which may be acid-treated; (3) a crystalline zeolitic aluminosilicate,either naturally occurring or synthetically prepared such as FAU, MEL,MFI, MOR, MTW (IUPAC Commission on Zeolite Nomenclature), in hydrogenform or in a form which has been exchanged with metal cations; (4) aspinel such as MgAl₂O₄, FeAl₂O₄, ZnAl₂O₄, CaAl₂O₄; (5) asilicoaluminophosphate; and (6) combinations of materials from one ormore of these groups. The refractory support of the reforming catalystpreferably comprises an inorganic oxide, more preferably alumina. Inembodiments, the reforming catalyst used in the penultimate reformingstage includes platinum on an alumina-containing support.

Halogen may be incorporated into the catalyst by combining it with asource of halogen such as alkali or alkaline earth chlorides, fluorides,iodides or bromides. Other halogen sources include compounds such ashydrogen halide, e.g., hydrogen chloride, and ammonium halides, e.g.,ammonium chloride. The preferred halogen source is a source of chlorine.The amount of halogen source combined with the catalyst should be suchthat the catalyst contains from about 0.1 to 3 wt % halogen, morepreferably from about 0.2 to about 1.5 wt % halogen, and most preferablybetween 0.5 to 1.5 wt % halogen.

The catalyst, if it includes a promoter metal, suitably includessufficient promoter metal to provide a promoter to platinum ratiobetween 0.5:1 and 10:1, more preferably between 1:1 and 6:1, mostpreferably between 2:1 and 5:1. The precise conditions, compounds, andprocedures for catalyst manufacture are known to those persons skilledin the art. Some examples of conventional catalysts are shown in U.S.Pat. Nos. 3,631,216; 3,415,737; and 4,511,746, which are herebyincorporated by reference in their entireties.

The reforming catalyst in the penultimate stage and final stage may beemployed in the form of pills, pellets, granules, broken fragments, orvarious special shapes, disposed as a fixed bed within a reaction zone,and the charging stock may be passed through in the liquid, vapor, ormixed phase, and in either upward, downward or radial flow.Alternatively, the reforming catalysts can be used in moving beds or influidized-solid processes, in which the charging stock is passed upwardthrough a turbulent bed of finely divided catalyst. However, a fixed bedsystem or a dense-phase moving bed system are preferred due to lesscatalyst attrition and other operational advantages. In a fixed bedsystem, the feed is preheated (by any suitable heating means) to thedesired reaction temperature and then passed into a reaction zonecontaining a fixed bed of the catalyst. This reaction zone may be one ormore separate reactors with suitable means to maintain the desiredtemperature at the reactor entrance. The temperature must be maintainedbecause reforming reactions are typically endothermic in nature.

The actual reforming conditions in the penultimate stage will depend, atleast in part, on the feed used, whether highly aromatic, paraffinic ornaphthenic and upon the desired octane rating of the product and thedesired hydrogen production.

The penultimate stage is maintained at relatively mild reactionconditions, so as to inhibit the cracking of the stream being upgraded,and to increase the useful lifetime of the catalyst in the penultimatestage. The naphtha boiling range feedstock to be upgraded in thepenultimate stage contacts the penultimate stage catalyst at reactionconditions, which conditions include a temperature in the range fromabout 800° F. (427° C.) to about 1100° F. (593° C.), a pressure in therange from about 70 psig (482 kPa) to about 400 psig (2760 kPa), and afeed rate in the range of from about 0.5 LHSV to about 5 LHSV. In someembodiments, the pressure in the penultimate stage is in the range fromabout 200 psig (1380 kPa) to about 400 psig (2760 kPa).

The effluent from the penultimate stage is an upgraded product, in thatthe RON has been increased during reaction in the penultimate stage ascompared to the RON of the naphtha feedstock. The penultimate stageeffluent comprises hydrocarbons and hydrogen generated during reactionin the penultimate stage and at least some of the hydrogen, if any,which is added to the feed upstream of the penultimate stage. Theeffluent hydrocarbons may be characterized as a mixture of C4−hydrocarbons and C5+ hydrocarbons, the distinction relating to themolecular weight of the hydrocarbons in each group. In embodiments, theC5+ hydrocarbons in the effluent have a combined RON of at least 85.

The effluent from the penultimate stage (otherwise termed the“penultimate effluent”) comprises C5+ hydrocarbons which are separatedinto at least an intermediate reformate and a heavy reformate. Theeffluent further comprises hydrogen and C4− hydrocarbons. In someembodiments, a hydrogen-rich stream is separated from the effluent in apreliminary separation step, using, for example, a high pressureseparator or other flash zone. C₄− hydrocarbons in the effluent may alsobe separated in a preliminary separation, either along with the hydrogenor in a subsequent flash zone. The intermediate reformate ischaracterized as having a lower mid-boiling point than that of the heavyreformate. In some embodiments, the intermediate reformate boils in therange from about 70° F. (21° C.) to about 280° F. (138° C.). In somesuch embodiments, the intermediate reformate comprises at least 70 vol %C5-C8 hydrocarbons. In some embodiments, the intermediate reformateboils in the range from about 100° F. (38° C.) to about 280° F. (138°C.). In some such embodiments, the intermediate reformate comprises atleast 70 vol % C6-C8 hydrocarbons. In some embodiments, the intermediatereformate boils in the range from about 100° F. (38° C.) to about 230°F. (110° C.). In some such embodiments, the intermediate reformatecomprises at least 70 vol % C₆-C₇ hydrocarbons. Recovery of anintermediate reformate fraction may be accompanied by the furtherrecovery of a largely C5 light reformate fraction. The light reformateis characterized as having a lower mid-boiling point than that of theintermediate reformate. In some embodiments, the light reformatefraction boils in the range from about 70° F. (21° C.) to about 140° F.(60° C.). In some such embodiments, the light reformate fractioncomprises at least 70 vol % C5 hydrocarbons. The heavy reformate that isproduced during separation of the upgraded product boils in the range ofabout 220° F. (14° C.) and higher. In some such embodiments, the heavyreformate comprises at least 70 vol % C9+ hydrocarbons.

The RON of the intermediate reformate is indicative of the mildreforming conditions in the penultimate stage. As such, the intermediatereformate typically has an RON within the range of about 65 to 90. Inone embodiment the intermediate reformate has a RON of 70 to 90. In afurther embodiment the intermediate reformate has an RON within therange of 70 to 85.

The reforming catalyst used in the final stage may be any catalyst knownto have catalytic reforming activity. Catalysts described above for thepenultimate stage can be used in the final stage. Examples of catalystsuseful in the final stage include: (1) molecular sieves such aszeolites, borosilicates, and silicoaluminophosphates; (2) amorphousGroup VIII metal catalysts with an optional promoter metal selected fromthe group consisting of a non-platinum Group VIII metal, e.g. rhenium,germanium, tin, lead, gallium, indium, and mixtures thereof; and (3)additional catalysts comprising acid catalysts and clays. The finalstage catalyst may include a single catalyst or a mixture of more thanone of the above catalysts. In an embodiment the final stage catalystcomprises a zeolite and a group VIII metal. In another embodiment thefinal stage catalyst is a platinum rhenium catalyst supported onalumina.

Molecular sieves particularly useful in the practice of the presentinvention include zeolites, zeolite analogs, and nonzeolitic molecularsieves. By “zeolite analog” it is meant that a portion of the siliconand/or aluminum atoms in the zeolite are replaced with othertetrahedrally coordinated atoms such as germanium, boron, titanium,phosphorus, gallium, zinc, iron, or mixtures thereof. The term“nonzeolitic molecular sieve” as used herein refers to molecular sieveswhose frameworks are not formed of substantially only silicon andaluminum atoms in tetrahedral coordination with oxygen atoms. Zeolites,zeolite analogs, and nonzeolitic molecular sieves can be broadlydescribed as crystalline microporous molecular sieves that possessthree-dimensional frameworks composed of tetrahedral units (TO4/2, T=Si,Al, or other tetrahedrally coordinated atom) linked through oxygenatoms. Depending on the identity of the T atoms in the zeolite, zeoliteanalog, or nonzeolitic molecular sieve the properties of the materialare affected. For example, the presence of aluminum in a zeoliteintroduces a negative charge in the zeolite framework and affects theacidity and activity of the zeolite as a reforming catalyst. The Si/Alratio in zeolites can vary from about 1 to infinity. The lower limitarises from the avoidance of neighboring tetrahedral units with negativecharges (Al—O—Al). It is generally accepted that the linking of two AlO₄tetrahedra is energetically unfavorable enough to preclude suchoccurrences. Negative charges in a zeolite, zeolite analog, ornonzeolitic molecular sieve framework are compensated by extraframeworkcations such as protons and alkali cations. The properties of zeolites,zeolite analog, or nonzeolitic molecular sieve can be altered throughexchange of these extraframework cations with other positively chargedspecies. The type of cations present in the zeolite, zeolite analog, ornonzeolitic molecular sieve framework help determine the acidity of themolecular sieve.

Strong acidity in the molecular sieve can be undesirable for catalyticreforming because it promotes cracking, resulting in lower selectivity.To reduce acidity, the molecular sieve preferably contains an alkalimetal and/or an alkaline earth metal. The alkali or alkaline earthmetals are preferably incorporated into the catalyst during or aftersynthesis of the molecular sieve. Preferably, at least 90% of the acidsites are neutralized by introduction of the metals, more preferably atleast 95%, most preferably at least 99%. In one embodiment, theintermediate pore molecular sieve has less than 5,000 ppm alkali. Suchintermediate pore silicate molecular sieves are disclosed, for example,in U.S. Pat. No. 4,061,724 and in U.S. Pat. No. 5,182,012. These patentsare incorporated herein by reference, particularly with respect to thedescription, preparation and analysis of silicates having a specifiedsilica to alumina molar ratio, having a specified crystallite size,having a specified crystallinity, and having a specified alkali content.

Prior art techniques have resulted in the formation of a great varietyof synthetic zeolites. Many of the zeolites have come to be designatedby letter or other convenient symbol, as illustrated by zeolite Z (U.S.Pat. No. 2,882,243); zeolite X (U.S. Pat. No. 2,882,244); zeolite Y(U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S. Pat. No. 3,247,195);zeolite ZK-4 (U.S. Pat. No. 3,314,752); zeolite ZSM-5 (U.S. Pat. No.3,702,886); zeolite ZSM-11 (U.S. Pat. No. 3,709,979); zeolite ZSM-12(U.S. Pat. No. 3,832,449); zeolite ZSM-20 (U.S. Pat. No. 3,972,983);zeolite ZSM-35 (U.S. Pat. No. 4,016,245); and zeolite ZSM-23 (U.S. Pat.No. 4,076,842). Zeolite Beta is described in U.S. Pat. No. 3,308,069 andRE 28,341 both to Wadlinger, and reference is made to these patents fora general description of zeolite Beta. The zeolite Beta of Wadlinger isdescribed as having a silica-to-alumina ratio going from 10 to 100 andpossibly as high as 150. Highly silicious zeolite Beta described ashaving silica-to-alumina ratios within the range of 20-1000 is disclosedin Valyocsik et al, U.S. Pat. No. 4,923,690.

In addition to cation-exchange, the catalytic properties of the zeoliticmolecular sieve can be altered by isomorphous substitution of at leastsome of the tetrahedral atoms to make zeolite analogs or nonzeoliticmolecular sieves wherein a portion or all of the silicon or aluminumatoms of the zeolite framework are replaced with, for example,germanium, titanium, boron, phosphorus, gallium, iron, or zinc. The useof these different elements in zeolite synthesis has often led tomaterials with novel topologies or to materials with properties that arevery different from their aluminosilicate (zeolite) counterparts whichhave equivalent framework topologies. For example, the aluminosilicatezeolite RHO cannot currently be synthesized with a Si/Al ratio muchbelow 3. However, the aluminogermanate and gallosilicate analogues ofzeolite RHO can be made with a Ge/Al ratio and a Si/Ga ratio of 1.0 and1.3 respectively. The cation-exchange capacities of these RHO materialsare therefore very different. Aluminophosphate and gallophosphateanalogues of zeolites are other example of molecular sieves based onreplacement of silicon with other atoms. These materials are usuallycomposed of strictly alternating AlO₄ (or GaO₄) and PO4 tetrahedralunits, but they can be altered by isomorphous substitution of silicon,magnesium, beryllium, or transition metal ions.

Molecular sieves have uniformly sized pores (3 to 10 Å) which aredetermined by their unique crystal structures. The pores in zeolites andzeolite analogs are often classified as small (8 T atoms), medium (10 Tatoms), large (12 T atoms), or extra-large (≧14 T atoms) according tothe number of tetrahedral atoms that surround the pore apertures.Zeolite A (LTA) and zeolite Rho are examples of molecular sieves withsmall pores delimited by 8-membered rings, wherein the pore aperturemeasures about 4.1 Å, while zeolite X (FAU) and zeolite Beta areexamples of zeolites with large pores delimited by 12-membered ringswherein the pore aperture measures about 7.4 Å. While the final stagecatalyst can comprise large pore molecular sieves such as zeolite X, ina preferred embodiment the final stage catalyst comprises a medium poremolecular sieve. The phrase “medium pore” as used herein means having acrystallographic free diameter in the range of from about 3.9 to about7.1 Angstrom when the molecular sieve is in the calcined form. Shapeselective medium pore molecular sieves used in some embodiments of thepractice of the present invention have generally 1-, 2-, or3-dimensional channel structures, with the pores characterized as being9 or 10-ring structures. The crystallographic free diameters of thechannels of molecular sieves are published in the “Atlas of ZeoliteFramework Types”, Fifth Revised Edition, 2001, by Ch. Baerlocher, W. M.Meier, and D. H. Olson, Elsevier, pp 10-15, which is incorporated hereinby reference.

Non-limiting examples of medium pore molecular sieves include ZSM-5,ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, ZSM-57, MCM-22, SSZ-20,SSZ-25, SSZ-32, SSZ-35, SSZ-37, SSZ-44, SSZ-45, SSZ-47, SSZ-57, SSZ-58,SSZ-74, SUZ-4, EU-1, NU-85, NU-87, NU-88, IM-5, TNU-9, ESR-10, TNU-10and combinations thereof.

The crystallite size of the molecular sieve can vary depending onpreparation conditions and may be tuned depending on the desired productand reactor conditions in the final stage of the reforming process. Byway of illustration only, in the medium pore zeolite ZSM-5, manipulatingcrystal size in order to change the selectivity of the catalyst has beendescribed in U.S. Pat. No. 4,517,402 which is incorporated herein byreference. Additional references disclosing ZSM-5 are provided in U.S.Pat. No. 4,401,555 to Miller, hereby incorporated by reference in itsentirety and in U.S. Pat. No. 5,407,558. In one embodiment, the finalstage catalyst is a high silica to alumina ZSM-5 having a silica toalumina molar ratio of at least 40:1, preferably at least 200:1 and morepreferably at least 500:1. In an embodiment the final stage catalyst ishigh silica to alumina ZSM-5 with a small crystallite size wherein thecrystallite size less than 10 microns, more preferably less than 5microns, and most preferably less than 1 micron.

Other molecular sieves which can be used in the final reforming stageinclude those as listed in U.S. Pat. No. 4,835,336; namely: ZSM-11,ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other similarmaterials such as CZH-5 disclosed in Ser. No. 166,863 of Hickson, filedJul. 7, 1980 and incorporated herein by reference.

SSZ-20 is disclosed in U.S. Pat. No. 4,483,835, and SSZ-23 is disclosedin U.S. Pat. No. 4,859,442, both of which are incorporated herein byreference.

ZSM-5 is more particularly described in U.S. Pat. No. 3,702,886 and U.S.Pat. Re. 29,948, the entire contents of which are incorporated herein byreference.

ZSM-11 is more particularly described in U.S. Pat. No. 3,709,979 theentire contents of which are incorporated herein by reference.

ZSM-12 is more particularly described in U.S. Pat. No. 3,832,449, theentire contents of which are incorporated herein by reference.

ZSM-22 is more particularly described in U.S. Pat. Nos. 4,481,177,4,556,477 and European Pat. No. 102,716, the entire contents of eachbeing expressly incorporated herein by reference.

ZSM-23 is more particularly described in U.S. Pat. No. 4,076,842, theentire contents of which are incorporated herein by reference.

ZSM-35 is more particularly described in U.S. Pat. No. 4,016,245, theentire contents of which are incorporated herein by reference.

ZSM-38 is more particularly described in U.S. Pat. No. 4,046,859, theentire contents of which are incorporated herein by reference.

ZSM-48 is more particularly described in U.S. Pat. No. 4,397,827 theentire contents of which are incorporated herein by reference.

Other zeolites useful in the practice of the present invention include,but are not limited to: Y zeolite, mordenite, offretite, omega,ferrierite, heulandite, SSZ-24, SSZ-25, SSZ-26, SSZ-31, SSZ-32, SSZ-33,SSZ-35, SSZ-37, SSZ-42, SSZ-44, EU-1, NU-86, NU-87, UTD-1, MCM-22,MCM-36, MCM-56, and mixtures thereof.

Examples of zeolite analogs useful in the process of the inventioninclude borosilicates, where boron replaces at least a portion of thealuminum of the zeolitic form of the material. Examples of borosilicatesare described in U.S. Pat. Nos. 4,268,420; 4,269,813; 4,327,236 toKlotz, the disclosures of which patents are incorporated herein.

Silicoaluminophosphates (SAPOs) are an example of nonzeolitic molecularsieves useful in the practice of the present invention. SAPOs comprise amolecular framework of corner-sharing [SiO4] tetrahedra, [AlO₄]tetrahedra and [PO₄] tetrahedra linked by oxygen atoms. By varying theratio of P/Al and Si/Al the acidity of the SAPO can be modified tominimize unwanted hydrocracking and maximize advantageous isomerizationreactions. Preferred molar ratios of P/Al are from about 0.75 to 1.3 andpreferred molar ratios of Si/Al are from about 0.08 to 0.5. Examples ofa silicoaluminophosphate useful to the present invention includeSAPO-11, SAPO-31, and SAPO-41, which are also disclosed in detail inU.S. Pat. No. 5,135,638.

The molecular sieves optionally include an amorphous support or bindersuch as amorphous alumina or amorphous silica. Other examples ofamorphous supports are selected from the group consisting of alumina,silica, titania, vanadia, chromia, zirconia, and mixtures thereof. Othersupports such as naturally occurring or synthetic clays including, butnot limited to, bentonite, kaolin, sepiolite, attapulgite, andhallyosite can be used in the process of this invention. The support maymake up to 80% by weight of the catalyst.

The molecular sieve catalysts according to the present invention mayalso contain one or more Group VIII metals, e.g., nickel, ruthenium,rhodium, palladium, iridium or platinum. The preferred Group VIII metalsare iridium, palladium, and platinum. Most preferred is platinum due toits high selectivity with regard to dehydrocyclization and stabilityunder the dehydrocyclization reaction conditions. The preferredpercentage of the Group VIII metals, such as platinum, in the catalystis between 0.1 wt. % and 5 wt. %, more preferably from 0.3 wt. % to 2.5wt. %.

Examples of amorphous Group VIII metal catalysts include those detailedin “penultimate zone catalyst” above. Suitable catalysts for the finalstage include platinum-containing amorphous reforming catalysts whichoptionally contain a promoter metal selected from the group consistingof a non-platinum Group VIII metal, e.g. rhenium, germanium, tin, lead,gallium, indium, and mixtures thereof. The platinum may exist within thecatalyst as a compound such as the oxide, sulfide, halide, oxyhalide, inchemical combination with one or more other ingredients of the catalyticcomposite, or as an elemental metal. Preferably, substantially all ofthe platinum exists in the catalytic composite in a reduced state. Thepreferred platinum component generally comprises from about 0.01 wt. %to 2 wt. % of the catalytic composite, preferably 0.05 to 1 wt. %,calculated on an elemental basis.

The catalyst can also include a binder material. Binders includeinorganic oxide supports such as alumina, silica, silica-alumina,titania, vanadia, chromia, zirconia, clays, zeolites, non-zeoliticmolecular sieves, and mixtures thereof. The binder may make up to 80% byweight of the catalyst.

Any conventional impregnation, mulling, ion exchange or other knownmethods for adding the metals to the binder may be used. The Group VIIInoble metals may be introduced into the amorphous binder by, forexample, ion exchange, impregnation, carbonyl decomposition, adsorptionfrom the gaseous phase, introduction during synthesis, and adsorption ofmetal vapor. The preferred technique is ion exchange or impregnation bythe so-called incipient witness method. Preparations of such catalystsare taught, e.g., in U.S. Pat. Nos. 3,415,737; 4,636,298; and 4,645,586,the disclosures of which are incorporated herein by references.

The catalyst optionally contains a halogen component. The halogencomponent may be either fluorine, chlorine, bromine, iodine or mixturesthereof. Chlorine is the preferred halogen component. The halogencomponent is generally present in a combined state with theinorganic-oxide support. The halogen component is preferably welldispersed throughout the catalyst and may comprise from more than 0.2wt. % to about 15 wt. %, calculated on an elemental basis, of the finalcatalyst.

Conventional acid catalysts such as solid acid catalyst including, butnot limited to, acidic clays and acidic zeolites may also be used in thepractice of the present invention as a final stage catalyst or as acomponent of the final stage catalyst. The zeolite molecular sievesdiscussed above with protons as counterions in the anionic zeoliteframework are examples of solid acid catalysts. MCM-22 is an example ofa layered aluminosilicate clay which can act as a solid acid.

The final stage catalyst may comprise acidic or non acidicphyllosilicate clay compositions derived from the smectites such asthose described in U.S. Pat. Nos. 4,248,739 and 5,414,185. Final stagecatalysts may comprise any natural or synthetic clays having a lamellarstructure, examples of which include, but are not limited to, bentonite,montmorillonite, berdellite, hectorite, vermiculite and the like.Layered clays can be delaminated or pillared to produce high surfacearea materials with a majority of their active sites or cations exposedat the crystal surface.

The clays may further comprise active metals such as Group VIII metals,preferably platinum or palladium. The clays mentioned above may be usedalone or admixed with inorganic oxide matrix components such as silica,alumina, silica-alumina, hydrogels and other clays. The clays may be anysuitable size or shape as to ensure good contact with the reactants.Examples include powder, pellets, granules, extrudates, and spheres.

The final stage catalyst is selected to provide a high selectivity forthe production of aromatic compounds at a reduced pressure, whichincreases the selectivity of C₆ to C₈ paraffin dehydrocyclization whilemaintaining low catalyst fouling rates. In embodiments, the final stagecatalyst comprises at least one medium pore molecular sieve. Themolecular sieve is a porous inorganic oxide characterized by acrystalline structure which provides pores of a specified geometry,depending on the particular structure of each molecular sieve. Inembodiments, the medium pore molecular sieve is a zeolite, which is acrystalline material that possess three-dimensional frameworks composedof tetrahedral units (TO_(4/2), T=Si, Al, or other tetrahedrallycoordinated atom) linked through oxygen atoms. An medium pore zeolitethat is useful in the present process includes ZSM-5. Various referencesdisclosing ZSM-5 are provided in U.S. Pat. No. 4,401,555 to Miller.Additional disclosure on the preparation and properties of high silicaZSM-5 may be found, for example, in U.S. Pat. No. 5,407,558 and U.S.Pat. No. 5,376,259.

A type of ZSM-5 that is useful includes a silicate having a form ofZSM-5 with a molar ratio of SiO2/M₂O₃ of at least 40:1, or at least200:1 or at least 500:1, or even at least 1000:1, where M is selectedfrom Al, B, or Ga. In embodiments, the ZSM-5 has a silica to aluminamolar ratio of at least 40:1, or at least 200:1, or at least 500:1, oreven at least 1000:1. A type of ZSM-5 that is useful further ischaracterized as having a crystallite size of less than 10 μm, or lessthan 5 μm or even less than 1 μm. Methods for determining crystallitesize, using, for example Scanning Electron Microscopy, are well known. Atype of ZSM-5 that is useful is further characterized as having at least80% crystallinity, or at least 90% crystallinity, or at least 95%crystallinity. Methods for determining crystallinity, using, forexample, X-ray Diffraction, are well known.

Strong acidity is undesirable in the catalyst because it promotescracking, resulting in lower selectivity to C5+ liquid product. Toreduce acidity, a type of ZSM-5 that contains an alkali metal and/or analkaline earth metal is useful for reforming the hydrocracked naphtha.The alkali or alkaline earth metals may be incorporated into thecatalyst during or after synthesis of the molecular sieve. Suitablemolecular sieves are characterized by having at least 90% of the acidsites, or at least 95% of the acid sites, or at least 99% of the acidsites being neutralized by introduction of the metals. In oneembodiment, the medium pore molecular sieve contains less than 5,000 ppmalkali. Such molecular sieves are disclosed, for example, in U.S. Pat.No. 4,061,724, in U.S. Pat. No. 5,182,012 and in U.S. Pat. No.5,169,813. These patents are incorporated herein by reference,particularly with respect to the description, preparation and analysisof molecular sieves having the specified silica to alumina molar ratios,having a specified crystallite size, having a specified crystallinityand having a specified alkali content.

Other medium pore molecular sieves that are useful for reforming includehigh silica to alumina mole ratio types of ZSM-11 and crystallineborosilicates. ZSM-11 is more particularly described in U.S. Pat. No.3,709,979, the entire contents of which are incorporated herein byreference. The crystalline molecular sieve may be in the form of aborosilicate, where boron replaces at least a portion of the aluminum ofthe more typical aluminosilicate form of the molecular sieve.Borosilicate molecular sieves are described in U.S. Pat. Nos. 4,268,420;4,269,813; 4,327,236 to Klotz, the disclosures of which patents areincorporated herein, particularly those disclosures related toborosilicate preparation.

The final stage catalyst further contains one or more Group VIII metals,e.g., nickel, ruthenium, rhodium, palladium, iridium or platinum. Inembodiments, the Group VIII metals include iridium, palladium, platinumor a combination thereof. These metals are more selective with regard todehydrocyclization and are also more stable under the dehydrocyclizationreaction conditions than other Group VIII metals. When employed in thefinal stage catalyst, these metals are generally present in the range ofbetween 0.1 wt. % and 5 wt. % or between 0.3 wt. % to 2.5 wt. %. Thecatalyst may further comprise a promoter, such as rhenium, tin,germanium, cobalt, nickel, iridium, tungsten, rhodium, ruthenium, orcombinations thereof.

In forming the final stage catalyst, the crystalline molecular sieve ispreferably bound with a matrix. The matrix is not catalytically activefor reforming or other hydrocarbon conversion. Satisfactory matricesinclude inorganic oxides, including alumina, silica, naturally occurringand conventionally processed clays, such as bentonite, kaolin,sepiolite, attapulgite and halloysite. Such materials have few, if any,acid sites and therefore have little or no cracking activity.

Reaction conditions in the final reforming stage are specified toeffectively utilize the particular performance advantages of thecatalyst used in the stage. Preferably the reaction pressure of thefinal reforming stage is less than the pressure in the penultimatestage. Low pressure in the final stage may lead to increased catalystfouling. However, as the process of the invention requires at least twostages—a penultimate and a final stage—catalyst regeneration in thefinal stage reactor can occur as needed to maintain high catalystactivity in the final stage. For example, as naphtha reforming is takingplace in the penultimate reactor, catalyst regeneration can take placein the final reactor. While the final stage catalyst is beingregenerated, the severity of the penultimate stage can be temporarilyincreased to meet RON targets for the total blended reformate whichwould otherwise be achieved with both the penultimate and final stagesin operation. Operating the final reforming stage at a lower relativepressure than the penultimate stage minimizes the formation of light(C₄−) products while increasing the yield of high octane naphtha andoverall liquid yield in the two stage process of the invention. Becausethe penultimate stage is operated at relatively mild conditions,catalyst life in that stage is lengthened while giving good yields ofdesired high octane products.

The naphtha feed to the final stage is the intermediate reformate whichis separated from the effluent of the penultimate stage. In the process,the intermediate reformate contacts the catalyst in the final stage atreforming reaction conditions, which reaction conditions include atemperature in the range from about 800° F. to about 1100° F. (427° C.to 593° C.), a pressure in the range from about 40 psig to about 400psig (276 kPa to 2760 kPa) to and a feed rate in the range of from about0.5 LHSV to about 5 LHSV. In some embodiments, the pressure in the finalreforming stage is less than 100 psig (690 kPa). Preferably the pressurein the final reforming stage is from about 40 psig (276 kPa) to about200 psig (1380 kPa), and more preferably from about 40 psig (276 kPa) toabout 100 psig (690 kPa). Hydrogen is preferably added as an additionalfeed to the final reforming stage, but it is not required. Inembodiments, hydrogen added with the feed is recovered from the processand is recycled to the final stage.

Depending on the particular process, the effluent from the finalreforming stage may contain light (i.e. C₄− products and/or hydrogen)products which may be removed from the reformate prior to furtherprocessing or blending to make a fuel product. The C₅+ reformate, hereinreferred to as the final reformate, which is produced in the finalreforming stage has an increased RON relative to that of theintermediate reformate which is the feed to the final reforming stage.Preferably, at least 75 vol % of the final reformate boils in the C₅+range. The final reformate may be used as a fuel or a fuel component byblending with other hydrocarbons. In embodiments, the RON of the finalreformate is 80 or higher, or 90 or higher, or 95 or higher.

The reformate is useful as a fuel or as a blend stock for a fuel. Insome embodiments, at least a portion of the reformate from the finalreforming stage is blended with at least a portion of the heavyreformate, which is recovered from the penultimate reforming stage; theblend may be used as a fuel or as a blend stock for a fuel.

Depending on the particular process, the effluent (otherwise termed the“final effluent”) from the final reforming stage may contain light (i.e.C₄− products and/or hydrogen) products which may be removed from thereformate in a final separation step prior to further processing forblending or use as a fuel. A hydrogen-rich stream may be separated fromthe effluent prior to the separation step, using, for example, a highpressure separator or other flash zone. C₄− hydrocarbons in the effluentmay also be separated in a preliminary flash zone, either along with thehydrogen or in a subsequent flash zone. The reformate which is producedin the final reforming stage has an increased RON relative to that ofthe intermediate reformate which is the feed to the final reformingstage. In embodiments, the RON of the final reformate is greater than 90or at least 95, or at least 98. In some embodiments, the final reformateboils in the range from about 70° F. (21° C.) to about 280° F. (138°C.). In some such embodiments, the final reformate comprises at least 70vol % C₅-C₈ hydrocarbons. In some embodiments, the final reformate boilsin the range from about 100° F. (38° C.) to about 280° F. (138° C.). Insome such embodiments, the final reformate comprises at least 70 vol %C₆-C₈ hydrocarbons. In some embodiments, the final reformate boils inthe range from about 100° F. (38° C.) to about 230° F. (110° C.). Insome such embodiments, the final reformate comprises at least 70 vol %C₆-C₇ hydrocarbons. In addition to the final reformate stream, a finallight stream may also be recovered from the final effluent. In suchcases, the final light stream boils in the range of about 70° (21° C.)to about 140° F. (60° C.). In some such embodiments, the final lightstream comprises at least 70 vol % C₅ hydrocarbons.

The reformate is useful as a fuel or as a blend stock for a fuel. Insome embodiments, at least a portion of the reformate from the finalreforming stage is blended with at least a portion of the heavyreformate, which is recovered from the penultimate reforming stage; theblend may be used as a fuel or as a blend stock for a fuel.

The gradual accumulation of coke and other deactivating carbonaceousdeposits on the catalyst will eventually reduce the activity and/orselectivity of the catalyst. Typically, catalyst regeneration becomesdesirable when from about 0.5 to about 5.0 wt. % or more of carbonaceousdeposits are laid down upon the catalyst. At this point, it is typicallynecessary to take the hydrocarbon feedstream out of contact with thecatalyst and purge the hydrocarbon conversion zone with a suitable gasstream. Catalyst regeneration can then performed either by unloading thecatalyst from the conversion zone and regenerating in a separate vesselor facility or performing regeneration in-situ. Alternatively, thecatalyst may be continuously withdrawn from the reactor for regenerationin a separate vessel, to be returned to the reactor as in a ContinuousCatalytic Reformer. Preferably, the catalyst is regenerated in situ.

Various regeneration procedures are known in the art. Generally, thetemperature of the final stage catalyst is gradually lowered to belowthe temperature of regeneration. The final stage reformer is takenoffline, for example by the use of a valve. The penultimate reformercontinues to operate at reforming reaction conditions, and to produceboth a hydrocarbon product of the desired RON as well as hydrogen whilethe final stage is bypassed. However, reforming severity in thepenultimate stage is increased so that the intermediate reformate has anRON of at least 90 or at least 95 or even at least 98. In embodiments,the reforming temperature in the penultimate stage is increased by atleast 5° F. (2.8° C.), or by at least 10° F. (5.6° C.) or even by atleast 15° F. (8.3° C.) while regenerating the final stage catalyst. Inembodiments, the reforming pressure in the penultimate stage isdecreased by at least 10 psig (69 kPa), or at least 20 psig (138 kPa) oreven at least 30 psig (207 kPa) while regenerating the final stagecatalyst. During regeneration, the intermediate reformate bypasses thefinal stage, and to be used, for example, as a fuel or fuel blendstock.Likewise, hydrogen which is recovered from the penultimate stagebypasses the final stage, to be used, for example, in other refineryprocesses.

The final stage catalyst is then regenerated by depressurizing the finalstage reactor, purging the final stage reactor with nitrogen, and thenintroducing a low level of oxygen, generally between 0.1 to 2%, andpreferably between 0.5 to 1%. The temperature of the final stage israised to initiate a carbon burn to remove coke deposits. Duringcatalyst regeneration, the coked catalyst is contacted with apredetermined amount of molecular oxygen. A desired portion of the cokeis burned off the catalyst, restoring catalyst activity. Flue gas formedby combustion of coke in the catalyst regenerator may be treated forremoval of particulates and conversion of carbon monoxide, after whichit is normally discharged into the atmosphere. After the carbon burn thefinal stage reactor is purged with nitrogen, the temperature is reducedto below the start of run temperature, and the final stage is put backon-line, i.e. the effluent of the penultimate stage now flows throughthe final stage. The temperature of the final stage is gradually raisedto run temperature while the temperature of the penultimate stage isgradually lowered so as to maintain the desired RON of the final productcoming off of the final stage reactor. In accordance with the invention,the final stage catalyst does not undergo chloriding or other halogentreatment during regeneration. Preferably, the final stage catalystcomprises a medium pore zeolite and at least one noble metal. In anembodiment the final stage catalyst comprises ZSM-5, ZSM-11, andmixtures thereof. It is an object of the invention to minimize theamount of time the multi-stage reforming process is run without thefinal stage due to catalyst regeneration. It has been found thatavoiding a chloriding step during regeneration of the final stagecatalyst minimizes the time the multi stage reforming process is runwithout the final stage reactor during final stage catalystregeneration.

The regeneration is performed in a halogen-free environment. Byhalogen-free, it is meant that chlorine, fluorine, bromine, or iodine ortheir compounds including for example, hydrogen chloride, carbontetrachloride, ethylene dichloride, propylene dichloride, are not addedat anytime during the catalyst regeneration process. Halogen freemethods to regenerate reforming catalysts are known in the art. Forexample, U.S. Pat. No. 5,155,075 discloses a process for regenerating amedium pore zeolite catalyst and is herein incorporated by reference inits entirety. Regeneration of coked catalyst may be effected by any ofseveral procedures. The catalyst may be removed from the reactor of theregeneration treatment to remove carbonaceous deposits or the catalystmay be regenerated in-situ in the reactor. For example, the final stagereformer unit may be operatively connected with a source of oxidizinggas at elevated temperature. The catalyst is regenerated by burning offcoke, producing CO₂ and H₂O. Reactor effluent can be cooled in afeed/effluent exchanger and/or in an air cooler. Final cooling can occurin a trim cooler. The effluent then enters a separator. Gas is releasedfrom the separator to maintain system pressure through pressure-responseventing. By the time it reaches the separator, water vapor formed duringthe burn has condensed and is separated from the recycle gas. Becausewater vapor at high temperatures may damage the catalyst, a relativelylow separator temperature is generally maintained in order to minimizethe H₂O partial pressure in the recycle gas returning to the reactor. Inan embodiment the separator temperature can be between about 20°-90° C.,preferably between about 30°-70° C., and most preferably between about40°-50° C. at 800 kPa pressure.

In a typical regeneration process, the final stage reactor is brought upto pressure with an inert gas, preferably nitrogen. The reactor inlettemperature is gradually decreased to a temperature of from 140° C. tono more than about 420° C. Oxygen is then introduced into the reactor.The oxygen is typically derived from air and an inert gas serves as adiluent, such that oxygen concentration is from about 21 mole % oxygento a lower limit of about 0.1 mole % oxygen. Higher levels of oxygen maybe used in methods where oxygen is supplied in a more pure form such asfrom cylinders or other containing means. Typical inert gases useful inthe carbon burn step may include nitrogen, helium, carbon dioxide, andlike gases or any mixture thereof; nitrogen being preferred. Theregeneration gases should be substantially sulfur-free as they enter thereactor, and preferably contain less than 100 part per million by volumewater. Because the oxygen content determines the rate of burn, it isdesirable to keep the oxygen content low so as not to damage thecatalyst by overheating and causing metal agglomeration, while stillconducting the carbon burn step in a manner that is both quick andeffective. In an embodiment, the oxygen level in the inlet to theregeneration vessel is between 0.2 to 4.0 mole % In another embodiment,air or oxygen is injected at a controlled rate to give a maximum oxygenconcentration of between about 0.1% and up to about 2%, preferablybetween about 0.25% and up to about 1%, and most preferably betweenabout 0.5% and up to about 0.7% at the reactor inlet. The temperature isthen increased to facilitate coke removal through a “burn.” As burningbegins, a temperature rise of about 85° C. is generally observed. As theburn dies off the inlet temperature is raised to and maintain at about455° C. The pressure of the reactor can vary, but generally, a pressuresufficient to maintain the flow of the gaseous oxygen containing mixturethrough the catalyst zone is selected. Generally, pressures can rangefrom between about 1.0 to 50.0 atmospheres and preferably from about 2to about 15 atmospheres. A gas hourly space velocity of about 100 toabout 10,000 per hour, with a preferred value of about 500 to about5,000 per hour is generally used, although this can vary depending onthe catalyst and amount of coking.

When the main burn is completed, as evidenced by no temperature riseacross the catalyst bed, the temperature is raised over 500° C. and theO₂ content can be raised. In an embodiment the O₂ content is raised toat least 3%, preferably at least 4%, and more preferably at least 5%.This condition is held at least one hour (or until all evidence ofburning has ceased). Generally, the regeneration process continues for asufficient period of time such that the aromatization activity isrestored to within 20° F. (11° C.) of the aromatization activity thecatalyst possessed at the start of the previous run cycle. By the term“aromatization activity” we mean the extrapolated start of runtemperature where the run conditions and the feed as well as thearomatics yield are substantially the same as in the previous run cycle.The platinum on the catalyst remains sufficiently dispersed on thesupport to allow for an activity change of not more than 10° C. upontermination of the regeneration procedure, and return of the catalyst tohydrocarbon conversion service. Thus, the catalyst aromatizationactivity is based upon the temperature needed to achieve a desiredconstant aromatics production. Regeneration by the process of thepresent invention results in a catalyst which has an aromatizationactivity, as defined above, which is within 10° C. of the temperatureneeded in the previous run to achieve the same constant aromaticsproduction.

When the regeneration is complete, the temperature is reduced, generallyto less than 500° C., and the system purged free of O₂ with an inertgas, preferably nitrogen to displace the oxygen and any water therefrom.The exit gas is easily monitored to determine when the catalyst zone issubstantially free of oxygen and water. After the carbon burn-off andpurge, the catalyst is activated by treatment with hydrogen. In theinitial reduction step, the catalyst is contacted with a hydrogencontaining stream at a temperature of from about 150° C. to about 380°C. for a period of at least of about 0.1 to about 10.0 hours. Preferredconditions for the reduction step are from about 200° C. to about 320°C. for a period from about 0.1 to about 2.0 hours. The pressure and gasrates utilized in the reduction step are preferably very similar tothose above described in the carbon burn step. Following the initialreduction, the catalyst may be further reduced and dried by circulatinga mixture of inert gas and hydrogen while raising the temperature tobetween 480° and 540° C. In the reduction step, metallic components arereturned to their elemental state and the resulting regenerated catalystpossesses activity, and selectivity characteristics quite similar tothose occurring in a fresh catalyst.

After completing the reduction step, the temperature is lowered to 450°C. or less. The reforming process in which the catalyst is employed maybe resumed by charging the hydrocarbon feedstream to the catalyst zoneand adjusting the reaction conditions to achieve the desired conversionand product yields. The reactor is brought up to reaction pressure andthe temperature decreased to below the reaction temperature during themulti-stage reforming process. The final stage reactor is put backonline, i.e. at least a portion of the effluent from the penultimatereactor flows through the final stage reactor to produce a hydrocarbonproduct of the desired RON.

In order to avoid a metal re-dispersion step, the ultimate temperaturein the carbon burn regeneration procedure is generally less than 415°C., and preferably between 315° C. to 400° C. This procedure allows thecatalyst to be restored to an activity very close to that of the freshcatalyst, without noble metal agglomeration which would require a metalre-dispersion step. It is further preferred the carbon burn be initiatedat a temperature of less than about 260° C. and further that the recyclegas be dried to achieve a water concentration in the recycle gas of lessthan 100 ppm water, prior to the recycle gas entering the reformingreactor train.

Reference is now made to an embodiment of the invention illustrated inFIG. 1. A naphtha boiling range fraction 5 which boils within the rangeof 50° F. (10° C.) to 550° F. (288° C.) passes into the reaction stage10 at a feed rate in the range of about 0.5 hr⁻¹ to about 5 hr⁻¹ LHSV.Reaction conditions in the reforming stage 10 include a temperature inthe range from about 800° F. (427° C.) to about 1100° F. (593° C.) and atotal pressure in the range of greater than 70 psig (483 kPa) to about400 psig (2760 kPa).

The effluent 11 from the penultimate stage is an upgraded product, inthat the RON has been increased during reaction in the penultimate stage10. The penultimate stage effluent 11 comprises hydrocarbons andhydrogen generated during reaction in the penultimate stage and at leastsome of the hydrogen (if any) added to the feed upstream of thepenultimate stage. In the embodiment illustrated in FIG. 1, the effluentis separated in separation zone 20 into a hydrogen-rich stream 21, a C₄−stream 22, an intermediate reformate 26 and a heavy reformate 26. Inembodiments, this separation occurs in a single separation zone. Inother embodiments, this separation is done in sequential zones, with thehydrogen, and optionally the C₄− stream, separated in one or morepreliminary separation zones prior to the separation of the intermediatereformate 25 and the heavy reformate 26.

In the embodiment illustrated in FIG. 1, the intermediate reformate 25comprises a substantial amount of the C₅-C₈ hydrocarbons contained inthe effluent, with smaller quantities of C₄ and C₉ hydrocarbons. Atleast a portion of intermediate reformate 25 is passed to finalreforming stage 30. Heavy reformate 26 contains a substantial amount ofthe C₉+ hydrocarbons contained in the effluent 11, and has an RON ofgreater than 98, preferably greater than 100.

Intermediate reformate 25 is passed to final reforming stage 30 forcontact with a catalyst comprising platinum and at least one medium poremolecular sieve, at reaction conditions which include a temperature inthe range from about 800° F. (427° C.) to about 1100° F. (593° C.) and apressure in the range from about 50 psig (345 kPa) to about 250 psig(1725 kPa).

Effluent 31 from the final reforming stage is separated in separationzone 40, yielding at least a hydrogen-rich stream 41, a C₄− stream 42,and a final reformate stream 45. In embodiments, the final reformatestream boils in the C₅+ boiling range. As described above, thisseparation may take place in one, or multiple, separation zones,depending on the specific requirements of a particular process. In anembodiment, the final reformate stream 45 may be further combined withthe heavy reformate 26 before further processing or use as a fuel orfuel blend stock. Hydrogen-rich stream 41 is combined with hydrogen-richstream 21 before using in other refinery processes, and C₄− stream 42 iscombined with C₄− stream 22.

Reference is now made to an embodiment of the invention illustrated inFIG. 2. A naphtha boiling range fraction 5 which boils within the rangeof 50° F. (10° C.) to 550° F. (288° C.) passes into the reaction stage10 at a feed rate in the range of about 0.5 hr⁻¹ to about 5 hr⁻¹ LHSV.Reaction conditions in the reforming stage 10 include a temperature inthe range from about 800° F. (427°/c) to about 1100° F. (593° C.) and atotal pressure in the range of greater than 70 psig (483 kPa) to about400 psig (2760 kPa).

The effluent 11 from the penultimate stage is an upgraded product, inthat the RON has been increased during reaction in the penultimate stage10. The penultimate stage effluent 11 comprises hydrocarbons andhydrogen generated during reaction in the penultimate stage and at leastsome of the hydrogen (if any) added to the feed upstream of thepenultimate stage. In the embodiment illustrated in FIG. 2, the effluentis separated in separation zone 20 into a hydrogen-rich stream 21, a C₄−stream 22, a light reformate 23, an intermediate reformate 24 and aheavy reformate 26. In embodiments, this separation occurs in a singleseparation zone. In other embodiments, this separation is done insequential zones, with the hydrogen, and optionally the C₄− stream,separated in one or more preliminary separation zones prior to theseparation of the light reformate 23, the intermediate reformate 24 andthe heavy reformate 26.

In the embodiment illustrated in FIG. 2, the light reformate 23comprises a substantial amount of the C₅ hydrocarbons contained in theeffluent, with smaller quantities of C₄ and C₆ hydrocarbons. Theintermediate stream comprises a substantial portion of the C₆-C₈hydrocarbons contained in the effluent; the heavy reformate 26 containsa substantial amount of the C₉+ hydrocarbons contained in the effluent11. Intermediate reformate 24 is passed to final reforming stage 30 at afeed rate in the range of from about 0.5 hr⁻¹ to about 5 hr⁻¹ LHSV, forcontact with a catalyst comprising platinum and at least one medium poremolecular sieve, at reaction conditions which include a temperature inthe range from about 800° F. (427° C.) to about 1100° F. (593° C.) and apressure in the range from about 50 psig (345 kPa) to about 250 psig(1725 kPa). During regeneration of the final stage catalyst, theseverity of the penultimate stage can be increased to increase the RONof the intermediate reformate. The RON of the intermediate underincreased severity of the penultimate stage (i.e. increased temperatureand/or pressure) would meet the target RON of the final reformatestream.

Effluent 31 from the final reforming stage is separated in separationzone 40, yielding at least a hydrogen-rich stream 41, a C₄− stream 42, afinal C₅ stream 43 and a final reformate stream 44. In embodiments, thefinal reformate stream boils in the C₆+ boiling range. As describedabove, this separation may take place in one, or multiple, separationzones, depending on the specific requirements of a particular process.As shown in the embodiment illustrated in FIG. 2, the final reformatestream 44 is further combined with the heavy reformate 26 before furtherprocessing or use as a fuel or fuel blend stock, hydrogen-rich stream 41is combined with hydrogen-rich stream 21 before using in other refineryprocesses, C₄− stream 42 is combined with C₄− stream 22 and final C₅stream 43 is combined with C₅ stream 23.

The following examples are presented to exemplify embodiments of theinvention but are not intended to limit the invention to the specificembodiments set forth. Unless indicated to the contrary, all parts andpercentages are by weight. All numerical values are approximate. Whennumerical ranges are given, it should be understood that embodimentsoutside the stated ranges may still fall within the scope of theinvention. Specific details described in each example should not beconstrued as necessary features of the invention.

EXAMPLES

In the following examples, the RON values are calculated values, basedon RON blending correlations applied to a composition analysis using gaschromatography. The method was calibrated to achieve a differencebetween measured RON values, determined by ASTM D2699, and calculatedRON values of within ±0.8.

Example 1

A naphtha feed, with an API of 54.8 (0.76 g/cm³), RON of 53.3 and anASTM D-2887 simulated distillation shown in Table 1 was reformed in apenultimate stage using a commercial reforming catalyst comprisingplatinum with a rhenium promoter on an alumina support. The catalystcontained about 0.3 wt. % platinum, and about 0.6 wt. % rhenium on anextruded alumina support. Reaction conditions included a temperature of840° F., a pressure of 200 psig, a 5:1 molar ratio of hydrogen tohydrocarbon and a feed rate of 1.43 hr⁻¹ LHSV. The C₅+ liquid yield was92.7 wt %. The hydrogen production was 975 standard cubic feet perbarrel feed (0.16 m³ H₂/liter oil).

This C₅+ liquid product (penultimate effluent) collected from thepenultimate stage had an API of 46.6 (0.79 g/cm³), an RON of 89 and anASTM D-2887 simulated distillation as given in Table 2.

TABLE 1 Simulated Distillation of naphtha feed Temperature, Vol % ° F.(° C.) IBP 182 (83)  10 199 (93)  30 227 (108) 50 258 (126) 70 291 (144)90 336 (169) EP 386 (197)

TABLE 2 Simulated Distillation of the C5+ liquid product from thepenultimate stage (penultimate effluent) Temperature, Vol % ° F. (° C.)IBP 165 (74)  10 189 (87)  30 234 (112) 50 257 (125) 70 289 (143) 90 336(169) EP 411 (211)

Example 2

The C5+ liquid product from Example 1 was distilled into an intermediatereformate and a heavy reformate. The intermediate reformate was found torepresent 80 vol % of the C5+ liquid product from Example 1. Theintermediate reformate, had an API of 55.7 (0.76 g/cm3), an RON of 85and an ASTM D-2887 simulated distillation as shown in Table 3, and wasused as feed in a final reforming stage in Examples 3-6. The heavyreformate was found to represent 20 vol. % of the C5+ liquid productfrom Example 1. The heavy reformate had an API of 28.9 (0.88 g/cm3) andan RON of 105, and is further described in Table 4.

TABLE 3 Simulated Distillation of intermediate reformate Temperature,Vol % ° F. (° C.) IBP 168 (76)  10 190 (88)  30 235 (113) 50 240 (116)70 284 (140) 90 296 (147) EP 336 (169)

Example 3

The intermediate reformate produced in Example 2 was used as feed to thefinal reforming stage which used a ZSM-5 zeolite based catalystcomposited with 35% alumina binder material. The ZSM-5 had a SiO₂/Al₂O₃molar ratio of ˜2000 and was ion exchanged to the ammonium form beforeincorporating in a 65% zeolite/35% alumina extrudate. The extrudate wasimpregnated with 0.8% Pt, 0.3% Na, and 0.3% Mg by an incipient wetnessprocedure to make the final catalyst. The reaction conditions andexperimental results are listed in Tables 4 and 5.

Example 4

A product which was produced in the final stage reforming of theintermediate reformate in Example 3 was blended with the heavy reformate(Example 2) which was not subjected to the final stage reforming. Thetotal RON of C₅+, total C₅+ yield and total H₂ production of the blendedfinal product are given in Table 4 based on using the total C₅+penultimate effluent as feed (which is distilled into intermediatereformate and heavy reformate in Example 2). The results are compared tothose obtained from Comparative Example 1 where the total C₅+ productwas produced from the total C₅+ penultimate effluent as feed, withoutdistillation into an intermediate and heavy reformate.

Example 5

The intermediate reformate produced in Example 2 was contacted with theplatinum/rhenium on alumina based catalyst described in Example 1 in afinal reforming stage. The reaction conditions and experimental resultsare listed in Table 5 and compared with Example 3.

Example 6

The intermediate reformate produced in Example 2 is contacted with theplatinum/rhenium on alumina based catalyst described in Example 1 in afinal reforming stage wherein the final reforming stage pressure is lessthan 200 psig (1380 kPa). The final reforming stage is run at the sametemperatures, LHSV, and hydrogen to hydrocarbon ratio as in Example 5.The C₅+ liquid yield for Example 6 is higher than the C₅+ liquid yieldfor Example 5 at the same or similar RON. The higher C₅+ liquid yield ofExample 6 as compared to Example 5 illustrates the benefits of runningthe final stage at a lower pressure than the penultimate stage with aplatinum/rhenium on alumina catalyst.

Comparative Example 1

The total C₅+ product produced in Example 1, without distillation intoan intermediate and heavy reformate, was contacted with the ZSM-5 basedcatalyst of Example 3 in a final reforming stage at 930° F. (499° C.),80 psig (550 kPa), 2:1 molar ratio of hydrogen to hydrocarbon and 1.5hr⁻¹ LHSV feed rate. The C₅+ liquid yield was 89.9 wt. % and RON of theC₅+ liquid product from the final reforming stage was 97.4. The hydrogenproduction was 190 standard cubic feet per barrel feed.

TABLE 4 Comparison of results from Example 4 and Comparative Example 1Example 4 Comparative Example 3 Example 2 Example 1 FeedstockIntermediate Heavy Total C₅+ reformate reformate penultimate (Example 2,(Example 2, effluent Table 3) Table 3) (Example 1, Table 2) CatalystPt/Na/Mg/ZSM-5 Not subjected Pt/Na/Mg/ZSM-5 with alumina to the finalwith alumina binder stage binder reforming Temperature, ° F. 900    —930    Pressure, psig 80    — 80    LHSV, hr⁻¹ 1.5   — 1.5   Molar 2:1 —2:1 H₂/hydrocarbon Ratio RON of C₅+ 97.0 ⁽¹⁾ 105 ⁽²⁾ 97.4 ⁽³⁾ C₅+ Yield,wt % 92.7 ⁽¹⁾ 100 ⁽²⁾ 89.9 ⁽³⁾ H₂ Yield, scf/bbl 300 ⁽¹⁾   — 190 ⁽³⁾  feed Total RON of C₅+ 98.7 ⁽⁴⁾   97.4 ⁽³⁾ Total C₅+ Yield, wt % 94.2 ⁽⁴⁾  89.9 ⁽³⁾ Total H₂ Yield, 240 ⁽⁴⁾   190 ⁽³⁾ scf/bbl feed Notes to Table4: ⁽¹⁾ For Example 3: RON of C₅+, C₅+ yield and H₂ production of theproduct are given based on the intermediate reformate as feed. ⁽²⁾ ForExample 2: RON of C₅+ and C₅+ yield are given based on the heavyreformate which is not subjected to the final stage reforming. ⁽³⁾ ForComparative Example 1: RON of C₅+, C₅+ yield and H₂ production of theproduct are given based on the total C₅+ penultimate effluent as feed.⁽⁴⁾ For Example 4: Total RON of C₅+, total C₅+ yield and total H₂production are given based on the total C₅+ penultimate effluent as feed(which is distilled into intermediate reformate and heavy reformate inExample 2). The final product of Example 4 consists of a blend of (i)the product from the final stage reforming of the intermediate reformateand (ii) the heavy reformate which is not subjected to the final stagereforming.

Table 4 demonstrates the benefits of the present invention when usingthe intermediate reformate as the feedstock at lower reactiontemperature (900° F. vs. 930° F.) (482° C. vs/499° C.) by showingimproved hydrogen yield, higher C₅+ liquid yield and higher RON versusthe full boiling range C₅+ feedstock.

TABLE 5 Comparison of results from Example 3 and Example 5 Example 3Example 5 Catalyst Pt/Na/Mg/ZSM-5 Pt/Re with alumina binder with aluminabinder Feedstock Intermediate Intermediate Intermediate Intermediatereformate reformate reformate reformate (Example 2) (Example 2) (Example2) (Example 2) Temperature, ° F. (° C.) 900 (482) 950 (510) 910 (488) 940 (504) Pressure, psig (kPa)  80 (552)  80 (552) 200 (1380) (1380)LHSV, hr⁻¹ 1.5 1.5 1.5 1.5 Molar H₂/hydrocarbon 2:1 2:1 5:1 5:1 RatioRON of C₅+ 97.0 100.6 96.9 101.8 C₅+ Yield, wt % 92.7 88.4 88.9 85.2 H₂Yield, scf/bbl feed 300 430 130 175

Table 5 demonstrates a preferred embodiment of the present invention,wherein the pressure of the final stage reactor is lower than thepressure in the penultimate stage Improvements at the lower pressurewith the ZSM-5 based catalyst in terms of C5+ yield and hydrogenproduction at similar C5+RON are seen versus the Pt/Re catalyst athigher pressure.

1. A reforming process comprising: a. providing a naphtha to amulti-stage reforming system that includes a penultimate reforming stagecontaining a first reforming catalyst and a final reforming stagecontaining a second reforming catalyst; b. contacting the naphtha at afirst reforming temperature with the first reforming catalyst andproducing a penultimate effluent; c. contacting at least a portion ofthe penultimate effluent at a second reforming temperature with thesecond reforming catalyst and producing a final reformate having an RONof greater than 90; and d. regenerating the second reforming catalyst inthe final reforming stage while reforming the naphtha in the penultimatereforming stage and producing a third reformate from the penultimatereforming stage that has an RON of at least
 90. 2. The process of claim1, wherein step (b) comprises contacting the naphtha at a firstreforming temperature in the range of from 800° F. to 1100° F. (427° C.to 593° C.).
 3. The process of claim 1, wherein step (b) comprisescontacting the naphtha at a first reforming pressure in the range offrom 200 psig (1380 kPa) to 400 psig (2760 kPa).
 4. The process of claim1, wherein step (b) comprises contacting the naphtha with the firstreforming catalyst, which comprises platinum and rhenium on an aluminasupport.
 5. The process of claim 1, wherein step (c) comprisescontacting at least a portion of the penultimate effluent at a secondreforming temperature in the range of from 800° F. to 1100° F. (427° C.to 593° C.).
 6. The process of claim 1, wherein step (c) comprisescontacting at least a portion of the penultimate effluent at a secondreforming pressure in the range of from 40 psig (276 kPa) to 200 psig(1480 kPa).
 7. The process of claim 1, wherein step (c) comprisingcontacting at least a portion of the penultimate effluent with thesecond reforming catalyst comprising silicalite having a silica toalumina molar ratio of at least 200, a crystallite size of less than 10microns and an alkali content of less than 5,000 ppm.
 8. The process ofclaim 7, wherein step (c) comprises contacting at least a portion of thepenultimate effluent with the second reforming catalyst comprisingiridium, platinum, palladium or a combination thereof.
 9. The process ofclaim 1, wherein step (a) comprises providing the naphtha having an RONof less than
 75. 10. The process of claim 1, wherein step (c) furthercomprises: a. isolating an intermediate reformate from the penultimateeffluent, the intermediate reformate having an RON within the range of75 to 90; and b. contacting the intermediate reformate at the secondreforming temperature with the second reforming catalyst and producingthe final reformate having an RON of greater than
 90. 11. The process ofclaim 1, wherein step (c) comprises producing a final reformate havingan RON of at least
 95. 12. The process of claim 1, wherein step (d)comprises producing a third reformate having an RON of at least
 95. 13.The process of claim 1, wherein step (d) comprises reforming the naphthain the penultimate reforming stage at a temperature that is at least 5°F. higher than the first reforming temperature.
 14. The process of claim1, wherein regenerating the second reforming catalyst in step (d)comprises: a. ceasing the flow of intermediate reformate to the finalreforming stage; b. increasing the reforming temperature in thepenultimate reforming stage by at least 5° F. (2.8° C.) to produce athird reformate having an RON of at least 90; and c. regenerating thesecond reforming catalyst in the final reforming stage.
 15. The processof claim 14, wherein regenerating the second reforming catalyst in step(d) comprises: a. passing a nitrogen containing stream through thesecond reforming stage to remove at least a portion of the naphthacontained therein; b. passing an oxygen containing stream through thefinal reforming stage to remove at least a portion of the carbondeposited on the second reforming catalyst contained within the finalreforming stage; c. passing a nitrogen containing stream through thesecond reforming catalyst to remove at least a portion of the oxygencontained therein; d. reducing the temperature of the second reformingcatalyst within the final reforming stage to a temperature of less thanthe second reforming temperature; e. introducing at least a portion ofthe penultimate effluent to the final reforming stage; and f. increasingthe temperature of the second reforming catalyst to a temperature in therange of 800° F. to 1100° F. (427° C.-593° C.).
 16. The process of claim15, further comprising: h. reducing the reforming temperature in thepenultimate reforming stage by at least 5° F. (2.8° C.).